A Discussion of Theoretical Models of Anomalous Diffusion of Vapors in Polymers

Abstract

The “anomalous” or “non-Fickian” diffusion of micromolecular vapors in homogeneous macromolecular substrates, a subject to which V. Stannett and his collaborators have eminently contributed, continues to develop both experimentally and theoretically. New experimental data have led to novel interesting theoretical concepts and insights. Nevertheless, orderly progress in this, like in any other, field also requires reassessment of the older models in the light of the more recent data, just as new theoretical treatments must pay due regard to older data. This task has been neglected to some extent, although it is admittedly hampered by the fact that most published data are not usually available in sufficient detail. However, present models of “non-Fickian” diffusion have not progressed much beyond qualitative or semiquantitative applications, so that their comparison at this level is quite useful.